1. Field of the Invention
The present invention relates to a solenoid-type fuel injection valve mainly for use in a fuel supply system in an internal combustion engine, and particularly to an improvement of a solenoid-type fuel injection valve comprising a valve seat member having a valve seat and a valve bore provided through a central portion of the valve seat, a valve stem for opening and closing the valve bore by cooperation with the valve seat, an injector plate coupled to an outer end face of the valve seat member and having a plurality of fuel injection bores disposed around an axis of the valve bore, and a fuel diffusion chamber which is defined between the valve seat member and the injector plate and which is faced by the valve bore and all of the fuel injection bores.
2. Description of the Related Art
Such a solenoid-type fuel injection valve is already known, for example, as disclosed in Japanese Patent Application Laid-open No.11-70347.
In such fuel injection valve, the fuel injection bores are provided in the injection plate so that they are inclined to become farther radially from the axis of the valve bore at a more downstream location, and the angle of a fuel spray foam formed by the fuel injected from all the fuel injection bores are determined depending on such inclination angle.
When the fuel injection bores are provided in the injection plate so that they are inclined to become farther radially from the axis of the valve bore at the more downstream location, the directions of inclination of the fuel injection bores are different. For this reason, it is not easy to make the fuel injection bores and hence, it is extremely difficult to provide a spreading angle of a fuel spray foam, as desired.
Accordingly, it is an object of the present invention to provide a fuel injection valve of the above-described type, wherein the spreading angle of the fuel spray foam can be determined as desired, while facilitating the formation of the fuel injection bores.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a solenoid-type fuel injection valve comprising a valve seat member having a valve seat and a valve bore provided through a central portion of the valve seat, a valve stem for opening and closing the valve bore by cooperation with the valve seat, an injector plate coupled to an outer end face of the valve seat member and having a plurality of fuel injection bores disposed around an axis of the valve bore, and a fuel diffusion chamber which is defined between the valve seat member and the injector plate and which is faced by the valve bore and all of the fuel injection bores, wherein the plurality of fuel injection bores are formed in parallel to the axis of the valve bore, and the spreading angle of a fuel spray foam formed by the fuel injected from the fuel injection bores is determined depending on an axis distance between the valve bore and each of the fuel injection bores.
With the first feature, the spreading angle of a fuel spray foam formed by the fuel injected from the fuel injection bores is increased with an increase in axis distance between the valve bore and each of the fuel injection bores. This can be utilized to determine the spreading angle of the fuel spray foam as desired by determining only the axis distance between the valve bore and each of the fuel injection bores. Moreover, since the fuel injection bores are formed in parallel to the axis of the valve bore, they can be formed in a multi-axis manner in the injector plate, leading to a substantially enhanced productivity. Therefore, it is possible to provide the spreading angle of the fuel spray foam as desired, while facilitating the formation of the fuel injection bores.
According to a second aspect and feature of the present invention, in addition to the first feature, a relationship between the thickness t of the injector plate and the diameter d of each of the fuel injection bores is set at t/d less than 1.
With the second feature, the atomization of the fuel injected from each of the fuel injection bores can be promoted, while reducing the function of restricting the direction of the fuel injected from each of the fuel injection bores. The setting of the spreading angle of the fuel spray foam depending on the axis distance R between the valve bore and each of the fuel injection bores can be achieved further easily and properly by reducing the function of restricting the direction of the fuel injected from each of the fuel injection bores. Thus, it is possible to achieve the proper setting of the spreading angle of the fuel spray foam and the promotion of the atomization of the injected fuel simultaneously.
According to a third aspect and feature of the present invention, in addition to the first or second feature, each of the fuel injection bores is formed into a frustoconical shape with its diameter increased toward its downstream side.
With the third feature, it is possible to further promote the atomization of the injected fuel.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.